The present invention relates to a driving device using a vibrating body and in particular to a driving device suitable for driving lens groups provided in a lens barrel. Cameras having a variable focus length imaging lens (hereinafter called zoom lens) have been marketed. The zoom lens is made to change a focus length by moving a plurality of lens groups configuring an optical system to a desired position along an optical axis, to vary a distance between them.
There are two major methods to move the plurality of the lens groups along the optical axis. A method is that a lens frame is engaged with a straight moving guide and the lens frame moves straight by rotating a cam cylinder. The other method is that a shaft practically parallel to the optical axis is provided as a guide shaft for straight moving, a sleeve where the guide shaft penetrates is formed on the lens frame and the lens frame is slidably moved straight directly by a motor and a lead screw along the guide shaft.
The later method having the lens frame moved directly by the lead screw along the guide shaft can be made with a simple structure, thus, it is used for a lens barrel do not requires a collapsible mechanism. (for example, Patent document 1)
Also, there is known a driving device where alternative current is applied to a piezoelectric element to make a vibrating body vibrated, and a driven member is moved relatively thought a friction by repeating contact and break off alternatively to and from the vibrating body.
As an actuator for such device, there is know an actuator where as a vibrating body, two layer type piezoelectric elements arranged so as to cross displacement directions at a predetermined angle, are used, each element is driven by alternative voltage signal having a predetermined phase difference so that a drive member provided at an intersection of the displacement directions of the elements, moves to draw an elliptical orbit and the drive member rotates the driven member in contact with the drive member in a predetermined direction (for example, Patent document 2.)
Patent Document 1: Japanese Unexamined Patent Application Open to Public Inspection No. 2003-222946 (FIG. 2 to FIG. 6)
Patent Document 2: Japanese Unexamined Patent Application Open to Public Inspection No. 2001-190081
The method in the above Patent Document 1 where the lens frame is moved along the guide shaft directly by the motor and the lead screw, requires the motor and the screw for each lens to be moved, thus at least 2 motors are needed for zooming use and there is a problem that the lens barrel becomes bulky due to a volume of the motor.
Also, the actuator in the above Patent Document 2 can drive the cylindrical-shaped driven body in a high speed without noise, however since the vibrating body is provided on a circumference of the driven body, there is remained a room for further down sizing as the driving device.